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Google Invests in 'Utility-Scale' Solar Power

Yesterday we noted the difficulty of designing a data center that relies fully on solar power, given the energy demands of major data centers and capacity limitations of current solar technologies. Today Google (GOOG) announced that its foundation has made a $10 million investment in eSolar, which is working to develop "utility-scale" solar power.

eSolar describes its approach as a "market disrupting solar thermal power plant technology." Generation can be scaled from 25MW to over 500MW at energy prices competitive with traditional fossil fuels. The company, which ios based in Pasadena, Calif., intends to provide modular solar power plants that scale in increments of 25 megawatts.

Solar thermal power systems use reflected sunlight as a heat-source to drive electric generators. Unlike photovoltaic systems, which use semiconductor materials to directly convert sunlight into electrons, solar thermal systems use the sun's heat to create steam to power electric generators. This video demonstrates how the technology works.

Solar thermal power is not new, and is widely used widely used in residential applications, such as heating swimming pools. The largest example of solar thermal power is the SEGS (Solar Electricity Generating Systems) project in California's Mojave desert, which used 2.5 million square meter array of parabolic reflectors to create a generating capacity of 354 MW.

eSolar's approach uses a heliostat, an array of movable mirrors that can track the sun throughout the day and concentrate their heat on a collector tower. A 2003 study commissioned by the National Renewable Energy Laboratory (NREL) found that tower technology is slightly cheaper to generate than the parabolic trough technology used at SEGS.